Living with a mild hybrid car – is going MHEV worth it?

Mild hybrid cars now account for more than one in 10 car sales in Britain, but it’s not all that obvious when you're out on the road.

That's because unlike plug-in hybrids and fully electric cars, mild hybrids – or MHEVs, as they’re frequently called – don’t bear external charger ports as they don’t require plugging in.

Nor do they have big batteries located under the car’s floor or under the boot, because MHEVs are, as the name suggests, only mildly electrified.

Lots of manufacturers make them and lots of people are buying them, but are they really worth the extra cash?

To find out, we jumped into one of the top-selling mild hybrids in Britain – the Ford Fiesta EcoBoost Hybrid mHEV – and lived with it for a week. Y’know, to see whether it forced any use or lifestyle changes like conventional hybrids.

Ford’s smallest MHEV – or ‘mHEV’, as Ford prefers – shares its lightly electrified 1.0-litre EcoBoost engine with the identically-badged Focus and Puma models.

It drinks petrol like a non-hybrid car but adds a small amount of electric shove into the equation via a 48-volt system. Sounds good.

To the untrained eye, the EcoBoost mHEV is a traditional Fiesta with nothing especially noteworthy about it.

Well, aside from the fact that the latest Fiesta is a really very handsome car, especially in the sporty-looking ST-Line trim we're testing, with 18-inch alloys, aggressive bumpers and a cheeky spoiler to boot (pun intended).

The cabin is smart and well thought-out, with sporty dials and seats to match that exterior, but nothing that screams ‘hybrid’ or ‘electrified’.

It’s technically subtle, just like other MHEVs on the market, the lightly-electrified used Fiat 500, used Hyundai i20 and used Suzuki Swift Sport variants included.

That’s quite likely going to be a good thing by most people’s measures, because now that electrification is commonplace on UK roads – the latest official figures show that almost 40% of new car sales are for ‘alternatively-fuelled vehicles’, ie. hybrids of all types and proper EVs – there’s little need to shout about it.

Instead, the Fiesta EcoBoost mHEV, just like its mild hybrid rivals, gets on with the hard work in the background.

Technically speaking, that means its engine and a small electric motor, powered by a compact battery that’s not much bigger than a cereal box, share the effort without you knowing.

What that means in operation from the driver’s point of view is, well, absolutely nothing. You drive the mild hybrid Fiesta as you would a non-MHEV version.

But you do notice the extra muscle provided by the mHEV’s two-part engine system, because this Fiesta is properly nippy off the line, and it feels effortless from low revs.

Ford’s hatchback – along with the bigger Focus and taller Puma – has a fantastic manual gearbox that’s as rewarding to use as it is technically strong, but you can be lazier with the gears as the mild hybrid system takes up the load.

Best of all, this extra initial grunt is present at all speeds, so overtaking can be safer on country roads, and thanks to the electric battery’s self-charging, the petrol engine consistently has less work to do.

The mHEV’s official combined fuel economy (so that’s for mixed-driving scenarios) is 57.6 miles per gallon, and that seems entirely realistic.

Our predominantly urban drives (where economy is typically lower) saw us achieve an average of 47mpg without any effort or adjustments in driving style. On the motorway, we cruised in our 125hp car with more than 60mpg on the digital dial.

Admittedly, the more powerful 155hp version of the mHEV will shed a few miles per gallon here and there for its added grunt, but you’re still looking at a plus-50mpg average, which means infrequent visits to the fuel pump.

Of course, to anyone familiar with proper self-charging hybrids, or indeed plug-in hybrids, where engine-off running is possible, that economy figure will seem small.

Cars in those categories – think of the Toyota Prius, or e-badged used BMW models and used Audi options, to name a few – and more than 100mpg is possible in certain driving scenarios.

But those cars feel different to operate as their engines and electric motors more obviously juggle power between different sources.

The plug-in hybrids – aka PHEVs – obviously require a lifestyle change as you’ll need to charge them up to achieve their best potential.

Mild hybrids like the Fiesta EcoBoost mHEV, then, represent a small but worthwhile step towards full electrification for those who want to retain familiarity and simplicity in their car, while achieving greater fuel economy.

Alternatively, go for a Toyota Yaris Hybrid on cinch and prices start at little more than £10,000. Like that boosted MHEV fuel economy, that’s liable to put a big smile on your face.

Sam Sheehan